The defense mechanisms to protect the mammalian gastrointestinal (GI) tract from colonisation by bacteria are highly complex. The GI tract of most mammals are colonised by both native microflora and by invasive pathogenic micro-organisms. In a healthy state, these competing microflora are in a state of equilibrium. The well being of humans is closely related to diet and GI health, and maintenance of the intestinal microflora equilibrium in humans can result in healthier human beings.
The number and composition of the intestinal microflora tend to be stable, although age and diet may modify it. Gastric acidity, bile, intestinal peristaltis and local immunity are factors thought to be important in the regulation of bacterial flora in the small intestine of human beings. Often human GI disorders are linked to bacterial overgrowth and the production of enterotoxins by pathogenic bacteria. These factors disrupt the intestinal microflora equilibrium and can promote inflammation and aberrant immune responses. Accordingly, modification of the intestinal microflora equilibrium may lead to or prevent many GI disorders.
Recently, research has begun to highlight some valuable strains of bacteria obtainable by isolation from the gastrointestinal tract of mammals, such as humans, and their potential use as probiotic agents. Probiotics are considered to be preparations of bacteria, either viable or dead, their constituents such as proteins or carbohydrates, or purified fractions of bacterial ferments that promote mammalian health by preserving the natural microflora in the GI tract, and reinforcing the normal controls on aberrant immune responses.
It is believed by some that probiotic bacteria are more effective when derived from the species, or closely related species, intended to be treated. While several strains of probiotic bacteria have been elucidated, methods of use of these strains and their therapeutic efficacy has largely been limited to modulation of gastro-intestinal disorders in humans. As yet, there has not been much investigation into the potential for these organisms to beneficially affect physiological systems other than the gastrointestinal tract.